Methods of and apparatus for generating and transferring heat



N, JR 2,987,305

FOR GENERATING NG HEAT June 6, 1961 J. v. CALHOU METHODS OF AND APPARAND TRANSFE 4 Sheets-Sheet 1 Filed May 31, 1957 June 6, 1961 J v.CALHOUN, JR 2,987,305

METHODS OF AND APPARATUS FOR GENERATING AND TRANSFERRING HEAT Flled May31, 1957 4 Sheets-Sheet 2 'IIIIIIIIIIIIIIIII June 6, 1961 J. v. CALHOUN,JR

METHODS OF AND APPARATUS FOR GENERATING AND TRANSFERRING HEAT 4Sheets-Sheet 3 Filed May 31, 1957 June 6, 1961 J. v. CALHOUN. JR

METHODS OF AND APPARATUS FOR GENERATING AND TRANSFERRING HEAT 4Sheets-Sheet 4 Filed May 31, 1957 United States Patent Ofice 2,987,305Patented June 6, 19 61 2,987,305 METHODS OF AND APPARATUS FOR GENERAT-ING AND TRANSFERRING HEAT John V. Calhoun, Jr., Stratford, Pa., assignorto J. V. Calhoun Company, Bala-Cynwyd, Pa., a corporation ofPennsylvania Filed May 31, 1 957, Ser. No. 662,796 16 Claims. (Cl. 263-6) This invention relates to methods of an apparatus for the internalheating of hollow cylinders.

Hollow cylinders in the form of drums, rollers and the like have formany years been used in many industries with heat applied interiorlythereof as by steam and other heating mediums. In some instances it hasbeen proposed to place within the cylinder burners and to'burn fuelwithin the cylinder for heat transfer to the interior surface. Wherefuel has been burned within the cylinder, the heat transfer rates havebeen relatively low because of several factors. First, there isinherently present adjacent the inner surface of the cylinder relativelydead air which in itself forms the principal heat insulator and reducesthe rate of heat transfer. The withdrawal of the spent products ofcombustion represents a further problem and in the past has producededdy currents and other flow of products of combustion in directionsaway from the interior surface of the cylinder.

In accordance with the present invention, high rates of heat transfer tothe interior surface of hollow cylinders have been attained, transferrates as high as 30,000 B.t.u.s per hour per square foot of saidcylindrical surface. Such high rates of heat transfer have beenaccomplished by eliminating substantially entirely the dead air spaceadjacent the inner curved surface, the avoidance of any tendency of theflame and hot products of combustion to move away from the interiorsurface of the cylinder, and by the attainment of unexpectedly highefliciency in the COaIIEICCl'lOH transfer of heat from the gases to thecylinder w In carrying out the invention in one form thereof, a mixtureof fuel and air is directed at high veloo yat an angle to the interiorsurface and insuch angular relation that as the pro-mixed fuel isburned, there are developed tangential forces fromthe expanding gases,and products of combustion which maintain them against the concavesurface of the cylinder. The gases move alongthe curved surface of thecylinder in high-speed turbulent flow. By

reason of the high-speed flow and the constantly changing area wipedbythe gases, any dead air space is eliminated to such degree that itseflfeetv on heat transfer is inconsequential. Further to increase theattainable rates of heat transfer, the cylinder is rotated so thatitsjnner surface, moves in .counterllow with therapidly flowing productsof combustion toproduce turbulent flow adjacent the curved surface.Further to maintain the high-speed curved path of the hot gases, thereis provided an exhaust manifold having anjinlet means. spaced lengthwiseof the roll and under substantial negative pressure. In this mannerthere are withdrawn through the exhaust manifold the gases .while {theyare. disposed closely against the interior sur ac ofth h l ow y s{I'heyeylinder itself is-closed at its ends, and means are vprcwided,forrelative adjustment of the locations of the exhaust manifold andburnerv so that the angular spacing maybe .uaried while maintaining theflow of gases in close of transfer.

, By rotating the hollow cylinder 10 in a clockwise direction Forfurther objects and advantages of the invention, reference is to be hadto the following description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is an isometric View of'an embodiment of the invention withsupporting parts omitted;

FIG. 2 is a sectional view of the cylinder-heating arrangement of FIG.1; i

FIG. 3 is a sectional view, taken on the line 33 of FIG. 2, of apreferred modification of the cylinder-heating apparatus;

FIG. 4 is a sectional view taken on the line 44 of FIG. 3;

FIG. 5 is a sectional view taken on the line 5-5 of FIG. '3;

FIG. 6 is an isometric view of a fractional part of the burner andassociated apparatus; and

FIG. 7 diagrammatically illustrates a complete system of control of andoperation of'the cylinder-heating apparatus. 1

Referring to FIG. 1, the invention in one form has been shown applied toa hollow cylinder 10 of the type which may be utilized for the drying ofwebs and sheet material of many kinds and character, the idler rollersand threading mechanism for such material having been omitted in orderto simplify the drawings. Within the hollow cylinder 10 there is locateda burner 11 having a plurality of openings 12 distributed lengthwise ofthe cylinder 10 and located in close proximity to the concave interiorsurface 10a. A mixture of fuel, preferably gas and air, under pressure,is introduced by way of supply line13. The premixed fuel flowsjto theburner by way of pipes 14 and 15 into the burner manifold. Afterignition, the burning p're-mixed fuel under pressure is directedangularly to ward the internal surface 10a. The angle 0 has been shownin FIG. 2 as between a radial line or plane 16 extended from the axis ofthe cylinder through a burner opening 12 and a line 1'7 coaxial of theopening 12. Thus, it will be seen that each opening 12 directs theburning fuel in the form of a jet 12a angularly toward the inner surface10a. By reason of the angularity of the jets relative to the surface10a, the initialpressure with which the pre-mixed fuel is releasedthrough the openings 12, and the forces developed by the expanding,burning gals, substantial tangential forces are developed tending tomove the flame and products of combustion I upwardly andcounterclockwise of the internal surface 10a as viewed in It has beenfound that if fuel underpressure be burned in the form of a plurality ofangularly directed jets in the manner described, the forces resultingfrom the expansion of combustion gases developed as an incident tojtheburning of the fuel are substantial and are effective to move thecombustion gases along and in intimate convective heat transfer with theinterior surface 10a. In accordance with the present invention, theproduction of and the continual expansion of gases incident to theburning of fuel are so controlled, by means .of thedirected jets and theconstantly changing curved surface 10a, that there is produced along andadjacent that surface 10a what appears to be a confined region for theflow of the combustion gases. As will now be explained, there isproduced turbulent flow of the gases and products of combustion alongthe surface 10a. The products of combustion move in wiping engagementwithjsurface 10a with'the elimination of the dead air blanket whichwould otherwise be as viewed in FIG; 2, i.e., in counterflow'with thedirected streams of combustion gases, the heat ti'ansfer rate is furtherincreasedand the periphery of the drum as a whole is elevated to hightemperatures for application of heat "to webs and strip or sheetmaterial of all kinds.

If the surface region a now be considered, the layer of gases adjacentthat surface will be moving in a clockwise direction. These gases, astheir forward velocity decreases, will exhibit a pressure change inrespect to the forward moving gases. Thus, with some of the gases movingcounterclockwise and some clockwise, there will be induced rotary motionor swirls which will extend along the surface 10a and will contribute toa high turbulent flow which is a condition desired and attained formaximum convection transfer to the cylinder wall by way of the surface10a.

The length of the path of the force-directed flow of combustion gases isvaried in accordance with the rate of firing of the fuel, assuming thatair is always present in amount corresponding with the theoreticalamount needed for complete combustion of the fuel. The provisions madefor relative adjustment as between the burner 11 and a combustionwithdrawing head 18 will be later described in detail.

The exhausting head or manifold 18 has suction applied to it toestablish a region of low pressure in close proximity to the innersurface 10a and circumferentially spaced from the burner 11 fortangential withdrawal of the products of combustion while they are tosome degree force-held against the internal surface 10a. In this manner,there is minimized any tendency of the products of combustion to moveinto the interior region of the cylinder 10 and thereby to create eddycurrents which would interfere with the actions above described.

In addition to the forces developed by the expanding gases and theincreasing velocity of the gases as a result of combustion of the fuel,there are other forces developed which contribute to the high heattransfer rates attainable in accordance with the invention. Theexpanding gases are, by the constraint imposed by the curved surface10a, forced to move in a circular path. The result will be thedevelopment of centrifugal forces which areeifective on the gases, whichdo have mass, to move them toward and against the surface 10a. Thus,there is produced a thick moving blanket of hot products of combustionalong the heat-transferring area between the burner 11 and exhaustmanifold 18 which presses against a layer in turbulent flow in Contactwith surface 10a. The several factors mutually contribute to theattainable high rates of heat transfer.

With fuel supplied at relatively high rate, it has been found that theexhaust manifold 18 may be located at least 180 away from the burner 11,and with still higher rates of combustion of fuel, the self-generatedforces will be effective to maintain the gases in close proximity to theconcave surface 10a through more than 270 of its area.

7 Typical operating data for one embodiment of the invention will be.later set forth.

Further in accordance with the invention, the rate of 7 fuel deliveryfrom the burner 11 through the plurality of openings 12 is controlledlengthwise of the burner 11 for the production of a uniform temperaturefrom one end of the roll to the other. More particularly, the burneropenings, adjacent the respective ends of the cylinder,

' supply fuel at somewhat greater rates than the openings spaced fromthe ends.

In this manner, compensation 1s had for certain amount of heat loss nearthe respective ends of the cylinder. In practice it has been found thatthe temperature differential, taken along a line parallel to 7 enhanced.In connection with the indicated variation in temperature lengthwise ofthe roll, it is to be noted that 7 available measuring instruments arerelatively inaccurate 7 "as applied to rotating surfaces, and thus it isbelieved fthatthe; uniformity of the temperature, notwithstanding J. thehigh rates, is considerably better than that indicated.

Contributing to the' uniformity .of temperature lengthwise of the roll10 is the exhaust manifold 18, the entrance area of the inlet means 18aof which is adjusted for a uniform differential of pressure lengthwiseof the roll modified at the ends, however, to take care of the greaterrates of flow of fuel adjacent such end portions of the cylinder. Thisadjustment is desirable by reason of the additional fact that theexhaust pipe 19 is connected to the manifold 18 at a point nearer theleft-hand end than the right-hand end, as viewed in FIG. 1. Asuctionadjusting plate 32 fastened by a series of bolts 33 is providedwith slots so that the plate 32 may be inclined at an angle for agreater area at the right-hand .portion of the suction opening 18a thanat the left-hand end.

In the preferred form of the invention, as illustrated in FIG. 3, itwill be noted that the suction plate 32' is provided with inclined uppersurfaces 32a and 32b which meet in the region of the exhaust pipe 19,thus to provide a minimum cross-sectional area for the suction opening18a in the region of the pipe 19. The upper edge of plate 32 can be acurved surface if desired, though in practice it has been found thatproviding the angular shape of FIG. 3 will be satisfactory. Suction isapplied to the manifold 18 by way of pipes 19, 20 and 21. The pipe 21 isclosed at its inner end and has extending therefrom a bearing 23 in theform of a hollow cylinder which encloses a stub shaft 22 carried by theinner closed end of the fuel supply pipe 14. This bearing 23 andexternal bearing means (not shown in FIG. 1) provide for the angularadjustment of the suction head 18 relative to the burner 11.

Externally of the cylinder 10, the pipe 21 terminates in an elbow 26,from which there extends a flexible length of pipe 27, such for example,as a flexible steam coupling. This flexible steam coupling is shown witha curved portion which provides needed length for rotation of pipe 21and elbow 26 for angular adjustment of the exhaust manifold 18 relativeto burner 11. In practice, a flexible length of pipe 27 may readilyprovide for an angular adjustment of the manifold 18 through at least30, an amount adequate for most practical applications. Where a greaterangular adjustment is desired, it may be facilitated as shown in FIG. 7where pipe 21 nests within a second pipe 21b extending axially thereofas at 85b with suitable packing therebetween. With this arrangement, themanifold 18 may be moved to any angular position and without thelimitation by the flexible length of pipe 27.

To cool the exhaust gases, an air inlet 30 and valve 30a admit air as acooling fluid for mixture with the gases exhausted from the cylinder 10.The temperature requirements on the flexible pipe 27 and the subsequentdisposal piping and associated equipment connected to the pipe 31 arereduced by admitting the cooling air to the exhaust gases shortly afterleaving the cylinder 10.

7 Though not shown in FIG. 1, the branch inlet 30 includes rates.

a filter to prevent entry of any combustible matter into the hotcombustion gases. In some applications the exhaust gases may be utilizedas a by-product of the heating of the cylinder 10, since they aresubstantially oxygenjective of providing new methods and systems ofgenerating and transferring heat by means of an internally heatedcylinder or roll having exceptionally high heat transfer For example, inthe preferred modification illustrated in FIGS. 3-6, it will be observedthat the cylinder 10 is provided with a plurality of fins/35 whichareillustrated as ofwasher-like sha per Though they may be welded to theinner surface 10a, it is preferred that they be formed by machining andthus to be integral with the wall of the cylinder. The fins 35 perform anumber of functions. First, they greatly increase the heat transfer areain contact with the hot products of combustion flowing between theburner 11 and the exhaust manifold 18. The fins 35 additionallysubdivide the hot gases into a multiplicity of individual streams in theregion of surface a with the overall blanket of rapidly moving gasessuperimposed above the subdivided streams.

While the heat transfer rates are extremely high in the regions of thesurface 10a and of the fins 35, annular slots 36 and 37 provide heattransfer barriers to decrease the flow of heat toward the supportingheads 39 and 40. The slots 36 and 37 are of greater importance in the arrangement shown in FIG. 1 where there are not provided theflow-subdividing heat-transfer fins. In that modification, the hotproducts of combustion from the end-burner openings tend to expand alongsurface 10a and, accordingly, to transfer heat to the heads. In themodification of FIG. 3, the slots 36 and 37 may be omitted, providingthe burner openings 12 terminate short of the end-most fins. Thus, theend-most fins themselves establish heat barriers relative to the headsand act to prevent flow of gases endwise of the cylinder.

Because of the high rates of heat transfer and the great release of heatwithin the cylinder 10, provisions are made to minimize the temperaturerise of the bearings, thereby to avoid the need of cooling fluid forsuch bearings. As shown in FIG. 3, the-cylinder 10 is journaled inbearings 41 and 42 carried by supports 43 and 44. The heads 39 and 40have welded thereto cylindrical journals 45 and 46. The journals areprovided with closure members 45a and 46a. For purposes of increasingstrength and rigidity of the heads 39 and 40 a plurality of gussetplates 47 and 48 are welded to the respective heads 39 and 40 and tothejournals 45 and 46. The subassemblies comprising the journals 45 and46, the gusset plates 47 and 48, and the heads 39 and 40 provide theneeded strength to support the cylinder10 for rotation at any desiredspeed.

As best shown in FIGS. 3 and 4, openings 49 are provided between each ofthegusset plates 47. These openings, besides lightening the subassembly,provide heattrausfer barriers, that is to say, they decreasethe-crosssectional area of the path from which heat can flow from theperiphery of the cylinder 10 toward the journal 45 andbearing 41.

Further toreduce the'transfer of heat readily inwardly from theperiphery of drum 10, there are secured, FIGS. '3 and 5,'to*the' outerfaceof the-head 39 aplurality of heat flingers-'50. 'Similar'heatflingers 51 are secured to the head 40, FIG. 5. Each array of fingers 50and 51-is formed integrally with backing plates 52 and 53. As

shown inFIG. 5,'the heat flingers 51 are inclined with :respect'toradial lines and together form a fan-like structure-which produces flowof a large amount of air outwardly from the journal 46, FIG. 3, alongthe head 40. By thus, providing'for forced cooling of the head 40, thetemperature of the journal 46 and of bearing 42, FIG. 3, is maintainedwithin reasonable limits and within a range for whichthe bearing 42 maybe'operated without the needofcooling fluid. In some instances, it maybe desirable to. provide cooling fluid for the bearings. In such event,the features just described contribute to; a reduction ofthe amount ofavailable cooling fluid which need be utilized, and thus such featuresare of advantage, either with or without cooling of the bearings.

Further contributing to the dissipation of heat is the selection ofmaterials within the heat flow path. The heads 39 and 40 and the gussetplates 47 and 48 are preferably of a material havingalow heat-transfercoeflicient, such for example, asstainless steel, whereas theheatflingers 50 and 51 are-of a material having a high heat-transfercoeflicient, such for example, as aluminum.

Thus, in the multiplicity of heat-transfer pathsofhigh heatconductivity, there is a rapidly moving amount of cooling air to movethe heat conducted thereto outwardly and away from the journals 45 and46. In contrast, the heat-transfer path to the journals 45 and 46 is oflow heat conductivity. In this connection, it will be noted that theheat flingers 50 and 51 terminate short of the journal 46, FIG. 5, theannular space between their inner ends providing an inlet for the flowof air between them, that annular space being in close proximity withthe journal 46 and providing substantial cooling thereof.

While it may be considered that the multiplicity of gusset plates 47 and.48 within the cylinder would tend to increase the flow of heat to thejournals 45 and 46 to a point which would indicate their omission, suchis not the case. Aside from the required rigidity for the journalsubassembly, the effective flow path for heat is sufliciently reducedand the cooling adequate for reasonably low operating temperatures forthe bearings. Thus, an inspection of FIG. 4 reveals that in the regionbetween adjacent holes 49 there is a greatly restricted cross-sectionalarea for flow of heat. In this region between adjacent openings, theflingers are moving a substantial amount of cool ing air to transferfrom that region the heat conducted thereto. Accordingly, the flingers50 and 51 are securely fastened -to the heads 39 and 40 in said regionsbetween said openings 49 as by cap screws located within the aforesaidregions. These cap screws have not been shown in the drawings but extendthrough the heat flingers 51 on opposite sides of the location of theplates 47 and insure maximum rates of heat transfer from the heads tothe heat flingers and the cooling air moving through them.

As indicated above, the suction manifold 18 and the burner 11 areangularly adjustable relative to each other to control the length andarea of the flow path of gases against the inner surface 10a of cylinder10. For angular adjustment of burner 11, there is included in the supplyline 13, FIG. 3, for the pre-mixed fuel and air a length 13a of flexiblepipe-coupling, such for example, as used in steam lines. The flexiblecoupling 13a permits rotation of the pipe assembly extending to andsupporting the burner 11. As shown, the burner supply pipe 14 and theexhaust pipe 21 are provided with the bearing means 22 and 23 midway ofthe cylinder and also with supporting bearings 54 and 55. Preferably,clamping means 56and 57 in the form of set screws are provided inassociation with each of bearings 54 and 55 to hold in fixed angularposition the burner 11 and the exhaust manifold 18. To simplify theconstruction and for the use of standard parts, it will be seen fromFIG. 5 that the fuel supply line 14 extends in Off-center relationthrough the hollow journal 46. This provides the space needed forconductors 69 and 61 and for a fuel supply line 62 which extends to apilot burner'63. The offset relationship of pipe 14 is provided by anoffset 14a as between the pipe 14 and the elbow 64. Another offset 65 inline 14 brings the T-fitting 66 to a position concentric with thecylinder and with the supporting bearings.

It is to be understood that the burner assembly and the exhaust manifoldassembly may each be supported in cantilever fashion as by two externalbearings, FIG. 7. If so used, the plug and socket bearings '22, 23 maybe omitted.

Returning now to the burner assembly and referring particularly to FIG.6, it will be observed that the fuel line 62 terminates at the pilotburner 63 which projects a flame 63a along one or more of the openings12 of the burner 11. Included in the pilot burner 63 is an ignitiondevice 67 sometimes referred to as a sparkplug. High-voltage current issupplied to the device 67 by way of conductors 60, 69 and 68. Theconductors 60 and 69 are suitably insulated from their associatedsupporting structure as by ceramic spacers included in the supportingtube 70. To initiate operation, a control circuit (not shown) is closedto produce a spark within the pilot burner'63. 'This ignites thepre-mixed fuel'then flowing matically ignites in succession the streamsof fuel issuing from the adjacent openings. It will be observed that theflame 63a from the pilot burner 63 impinges upon a flame rod 71, whichflame rod is also disposed within the flame produced by the prc-mixedfuel issuing from one of the openings 12. The flame rod 71 isconventional. By change in itsresistance due to rise in temperature, a

1 safety circuit, including conductor 61 insulated by ceramic spacers,maintains open a fuel supply valve (such as valve 90, FIG. 7) and closesthat valve upon flame failure.

' ,,For an understanding of additional control features forming a partof this invention, reference will now be had to the operation as awhole.

Referring now to FIG, 7, it will be assumed that a motor 80 is, througha sprocket 81 and chain 82, driving a sprocket 83 secured to the hollowjournal 45 of the cylinder 10 for rotating "it at a selected speed. Themotor 80 may be a variable speed motor, or the speed of drum 10 may becontrolled through gears or other speed-changing mechanism.

With the cylinder 10 rotating at the speed desired for a web of paper orother material undergoing drying (such web being partially wrappedaround the cylinder 10 and a section of which is shown at 10w), thepre-mixed fuel and air will enter by way of the fuel pipe 14 aspreviously explained.

In FIG. 7, instead of illustrating the flexible section of pipe as shownin FIG. 3, overlapping lengths of pipe as indicated at 85a are to betaken as symbolic of an airtight rotatable connection between pipe 14and the supply pipe 14b. The pipe 14b includes a Venturi tube 86, and inconjunction with fuel mixing valve 87, of 35 conventional construction,adds fuel to the line 14b in fixed proportion to the rate of flow of airentering the Venturi as at the region 88. The fuel control valve 87includes a connection 89 responsive to the pressure at the low-pressuresection of the Venturi tube 86. As the flow of air through the Venturitube increases, so does the amount of fuel supplied from the line 13.The valve 90 is a safety shut-01f valve which for the operation nowbeing described will be considered fully open.

To simplify FIG 7, there have been omitted the pilot burner, the flamerod, and associated auxiliary control equipment which includes numerousinterlocking circuits which do not affect the operations so long as themotors and equipment are functioning normally. Upon the failure of anysignificant component, the system will automatically shut down.

The flow of air to the Venturi tube 86 is provided by an air blower 93provided with a filter 94 at the air inlet. The blower is driven by amotor 92. In the outlet line from the blower 93 a control valve 95 isutilized to vary the amount of air supplied to the burner 11. Though theair control valve 95 may be manually set to predetermine the rate ofcombustion within the cylinder 10, it has been illustrated as under thecontrol of a thermocouple 96 responsive to the temperature of thecylinder at a selected location on its external surface. The externaltemperature of the cylinder varies with change in heat load imposed byweb 10w.

The thermocouple 96 is included in a measuring circuit 97 of thepotentiometer type and which includes a variable resistor or slidewire98 and a detector 99 illustrated by the broken lines as driving apen-index relative to a chart and associated scale of a recorder 100.,The measuring circuit and indicator-recorder 100 may be of the typeillustrated in Williams Patent No. 2,113,164, dated April 5, 1938. Asthe temperature of the external surface of the roll 10 changes, thethermocouple 96 will respond, and the detector 99 will not only move thepenindex of the recorder 100, but through the mechanical connection 101will adjust the movable contact 102a of,

an input potentiometer 103 for introducing an input signal to anamplifier 104 which controls the 'energization of a motor 105 to adjustthe position of the control valve 95. Thus, the position of the movablecontact 102 with respect to its associated slidewire will always berepresentative of the temperature as measured by thermocouple 96'. r:The amplifier 104 and the motor 105 are representative of controlsystems of the' type disclosed in Davis Patout No. 2,666,170, datedJanuary'12, 1954, the input slidewire 102 corresponding with theslidewire 31 of that patent. It is to be noted that the control systemas represented by the amplifier 104 includes proportional, rate andreset actions. It will be preferred that the reset 'and rate actions beset at relatively low'values for the reason that other adjustments cantake place which may affect the positioning of the air control-valve 95.In this connection, it is to be noted that adjustment of the air controlvalve 95 effectively changes the fuel input to the cylinder 10.Accordingly, it is correct to say that the control system responsive tochange in the temperature of thermocouple 96 directly regulates the fuelinput to the cylinder 10. By functioning through and by means of the aircontrol valve 95, it is likewise assured that increased or decreasedamounts of fuel will be burned within the cylinder 10 with the properamount of combustion air for 100% combustion.

While the temperature of the external convex surface of the cylinder 10is measured at a single point, it is to be 0 remembered that thecylinder is rotated at relatively high A speed by the motor 80.Regardless of speed, the thermocouple 96 of the contact type measuresthe average temperature of the roll, which average temperature will beapproximately thesame throughout the circumference for anygiven instant.It is preferred that the thermocouple 96, or other roll-temperaturemeasuring device, be located within the combustion zone between theburner 11 and the exhaust manifold 18,, since. any change in the rate oftiring may be more quickly detected by the thermocouple. There will thenbe less lag in the control fimctions which have been partly set forth.It will now be assumed that the heat load imposed by e the web 10w onthe heat-generating and transferring cylinder 10 is such that the airvalve 95 is halfway between 'its maximum and minimum positions forproducing a temperatureas measured by the thermocouple 96 at the setpoint. In order to have a numerical illustration, it will be assumedthat the set point as established by a Y control-setter in amplifier l04(suchas the control point 'setter'42 of the aforesaid Davis patent) willbe 600 F., though it is to be understoodthe cylinder is capable of'operation at temperatures as high as 1200 F. If the temperaturedecreases, the valve 95' will be opened a greater amount. Since therewill be an increase in fuel delivery to the cylinder 10, it will bedeslrable immediately to increase the angular separation between theburner 11 and the exhaust manifold 18. The increased separation, asalready explained, will increase the amount ofheat transferred to thecylinder wall. Accordingly, 7 there is provided a control system forregulating the angularseparation between burner lland exhaust manifold18. This system, like the one disclosed in the aforesaid Davis patent,includes an'input slidewire 112. A ,movable c0ntact 112a is adjus ted inresponse to change in the flow of air through the'line 88. A flow meter113 is included in this line and through mechanical connections 114, 115drives, themovable contact 112a. Accordingly, the input signal to anamplifier 116 which coni trols'the energization'of a motor .117 has amagnitude [dependent upon the rate of flow of fuel to the cylinder 10.The motor'117, through a drive sprocket 120, a driving f chain 121, a;nda sprocket 122, rotates the burner 11 about 'fthe axis of cylinder10 tochange its angular position relative to the' e'xha'ust manifold '18If,desired, there may be provided a mechanical connection from motor 117as through the gears 123, a sprocket 124, a chain 125, and a sprocket126 for rotating the exhaust manifold 18 about the axis of cylinder forconcurrent adjustment to vary the angular separation between burner 11and manifold 18.

It may here be observed that the fuel and air line 14 extendstelescopically within fuel and air supply line 14b, the overlappingportion shown at 85a having suitable packing to prevent leakage. Asimilar arrangement is provided for the outlet or exhaust line 21 asindicated by the overlapping or telescopic relationship of the line 21with the line 2111 as indicated at the region 85!). It is to be furthernoted that there is provided a pair of bearings for the lines 14 and 21so that the burner 11 and the manifold 18 are both cantilever-supportedwithin cylinder 10.

While the arrangement of the lengths of flexible pipe as shown in FIG. 3will be preferred, the present arrangement has been illustrated toindicate a. further modification. When flexible couplings are includedto provide for the angular adjustment of the burner 11 and manifold 18,the limit switches of said Davis patent (as shown therein at 82 and 86)will be provided with each of them set for the respective limits ofrotation for the burner and manifold.

By increasing the area of the heat-transferring surface with increaseof'heat load on the cylinder 10 and as the fuel supply is increased totake care of that load, there will result a transfer of a greater amountof heat without substantial decrease in the efiiciency of operation ofthe system. More particularly, fora selected set point, for example, theaforesaid 600 F., there will be a dependent relation between variousheat loads imposed upon the cylinder 10 and the angular separationbetween the burner 11and the exhaust manifold 18. For a 50% heat load,the separation distance will be made the optimum, i.e., for maximumefliciency in terms of heat input to the cylinder. The control 116 willthereafter vary the angular separation to maintain high efiiciencieswith change in heat load in'either direction.

As fuel is'delivered to cylinder 10 at greater rate, the quantity of'products of'combustion will increase and it will, accordingly, bedesirable to increase the suction to the manifold 18, both to takeaccount of the larger quantity of combustion products as well as theincreased separation distance between burner 11 and suction manifold 18.Accordingly, as the heat load on the cylinder 10 is increased and thereis a resultant change inrate of flow of fuel, as indicated by a changein the rate of flow of air as detected by the flow meter 113, asuction-controlling valve 130 is automatically positioned to increasethe suction With increase of load and to decrease the suction withdecreaseofload. This adjustment is made automatically bymeans of'a'motor131 whose energization is under the control'of an amplifier 132 havingin its 'input'c'ircuita slidewire 133 with its movable contact 13311adjusted by way of the mechanical connection 114 extending from theliowm'e'ter113. In general, it will be preferred that the control system131-132 (like that of the aforesaid Davis patent) be primarily aproportional system, i.e., one that sets minimum suction for a minimiimrate of fuel delivery to the cylinder 10 and maxi- 'mum suction for amaximum rate of fuel delivery to the cylinder 18.

The control system of said Davis patent also includes an adjustment forthe extent of change of position of 'valve130 for a given change inoutput from the flow meter 113. Thus, the characteristics of aparticular o1i the cylinder at widely differing set point temperatures.

In "some instances, it "may be desirable automatically to position thevalve 30a in the cooling-air inlet line 30. In 'such event, athermocouple 150 responsive to the products of combustion issuing fromcylinder 10 can control the positioning of the valve by way of anamplifier 151 and a motor 152 which increases the opening of the valvewith increase of temperature and reduces the opening of the valve withdecrease of temperature. These provisions will be particularly desirablefor the fully automatic system of control.

It is to be understood that in many applications it will be entirelysatisfactory manually to set the angular relationship between burner 11and exhaust manifold 18, and likewise manually to position the suctionvalve and the cooling-air inlet valve 300, since the load changes whichmay occur through long periods of operation may not be sufficientlygreat as to justify the expense of the added control equipment.

From the foregoing, it will be seen that the variableareaheat-transferring apparatus may be manually, automatically, orsemi-automatically controlled, depending upon the requirements ofparticular applications. It is to be further understood that theelectrical control mechanisms illustrated may be replaced by pneumaticcontrol devices which are in general use in the combustion field. Theamplifier and control motors have been illustrated as symbolic ofconventional control mechanisms responsive to temperature and utilizedfor the positioning of valves and flow-controlling devices.

Where still higher rates of heat transfer are desired and for stillhigher temperatures, upwardly of about 900 F., it will be desirable toprovide fluid-cooled supply lines for the pre-r'nixed fuel and air,since the temperatures within the cylinder will be quite high. In otherWords, the fuel lines will be jacketed for circulation of cooling fluidto maintain the pre-mixed fuel and air below the combustion'point. Byreason of the high heat transfer rates attainable, there is realized aconsiderable reduction in the number of drying rolls required for agiven installation. For example, where 40 or 50 steam heated dryingrolls are now required in paper making, the number may be reduced to 15or 20 with a corresponding decrease in required floor space for a givenpaper-treating system.

In the preferred embodiment described above in connection with FIGS. 37,the cylinder had a diameter of 48", a length of 54". The cylinderrotated at 50 r.p'.m. It was this apparatus that has developed transferrates as high as 30,000 B.t.u.s per hour per square foot of cylindersurface and at unexpectedly high efficiency, approaching 70%. Thereference to each square foot of the cylinder surface is to the entireinternal cylindrical surface and is not limited to the area of theconcave surface over which the'hot combustion products flow. Where therequirements are for cylinders of still greater diameter, it iscontemplated that additional burners and suction heads may be provided,each pair to operate over a difierent segment of internal concavesurface, and each pair to be angularly adjustable as described aboveover its own Billocation of the curved heating member or cylinder.

What is claimed is:

1. The method of heating a hollow cylinder at rates not limited by thepresence of an insulating layer of air between the internal curvedsurface of said cylinder and products of combustion within saidcylinder, which comprises directing burning high velocity streams ofpremixed fuel and air at a substantial angle to the internal curvedsurface along'a path which is angularly displaced from a radius of saidcylinder for development of substantial forward velocity of all of saidburning fuel and air and in a zone extending lengthwise of the cylinderand in close proximity to said curved internal surface, constraining theflow path of the burning streams of premixed fuel and air along thecurved inner surface of the cylinder, whereby the initial-velocity ofsaid pre-mixed locity throughout a large circumferential area of thecylinder, applying suction across the arcuate path traversed by theproducts of combustion for withdrawing the products of combustiontangentially of said cylinder in a region extending lengthwise of saidcylinder and adjacent said surface, and regulating the angular spacingbetween the points of initiation of said burning streams and said regionof withdrawal in accordance with change in a variable affecting thetransfer of heat to said cylinder.

2. The method of heating a hollow cylinder at rates not limited by thepresence of an insulating layer of air between the internal curvedsurface of said cylinder and products of combustion within saidcylinder, which comprises directing burning high velocity streams ofpremixed fuel and air at a substantial angle to the internal curvedsurface along a path which is angularly displaced from a radius of saidcylinder for development of sub- 7 stantial forward velocity ofall ofsaid burning fuel and air and in a zone extending lengthwise of thecylinder and in close proximity to said curved internal surface,constraining the flow path of the burning streams of premixed fuel andair along the curved inner surface of the cylinder, whereby the initialvelocity of said pre-mixed fuel and air and the expansion of the gasesincident to :tween the internal curved surface of said cylinder andproducts of combustion within said cylinder, which comprises directingburning high velocity streams of pre mixed fuel and air at a substantialangle to the internal curved surface along a path which is angularlydisplaced from a radius of said cylinder for development of substantialforward velocity of all of said burning fuel and air and in a zoneextending lengthwise of the cylinder and in close proximity to saidcurved internal surface,

constraining the flow path of the burning streams of premixed fuel andair along the curved inner surface of the cylinder, whereby the initialvelocity of said pre-mixed fuel and air and the expansion of the gasesincident to the combustion thereof maintains the high initial velocitythroughout a large circumferential area of the cylinder, applyingsuction across the arcuate path traversed by the products of combustionfor withdrawing the products of combustion tangentially of said cylinderin a region extending lengthwise of said cylinder and adjacent saidsurface, concurrently regulating the angular spacing between the pointsof initiation of said burning streams and said region of withdrawal, andvarying the suction pressure at the region of withdrawal in accordancewith change in said flow of fuel and air. v

4. The method of heating a hollow cylinder at high rate I whichcomprises directing a plurality of streams of buming pre-mixed fuel andair along the length of the cylinder and in close proximity to theinternal curved surface thereof and at an angle to said internal curvedsurface for developing tangentially directed forces to maintain the hotproducts of combustion along and in intimate contact with said internalcurved surface, rotating said cylinder in a direction opposite to thedirected travel path of said flame and hot products of combustion toincrease the 7 rate of transfer by convection of heat to said hollowcylinder by way of the internal curved surface thereof, withdrawingtangentially of the cylinder the products of combustion in a region ofreduced pressure and adjacent said inner curved surface, and regulatingthe spacing between'the points of initiation of said streams and said 12region of low pressure to produce continuous flow of the products ofcombustion along said internal curved surface and thence into saidregion of low pressure.

5. The method of heating a hollow cylinder at rates not limited by thepresence of an insulating layer of air between the internal surface ofsaid cylinder and products of combustion within said cylinder, whichcomprises directing burning high velocity streams of pre-mixed fuel andair at a substantial angle to the inner surface along a path which isangularly displaced from a radius of said cylinder for development ofsubstantial forward velocity of all of said burning fuel and air and ina zone extending lengthwise of said cylinder and in close proximity tosaid internal surface, constraining the flow path of the buming streamsof pre-mixed fuel and air along the curved inner surface of thecylinder, whereby the initial velocity of said pre-mixed fuel and airand the expansion of the gases incident to the combustion thereofmaintains the high initial velocity throughout a large circumferentialarea of the cylinder, rotating said cylinder to move said internalsurface in counterflow to that of all of said products of combustion toproduce a turbulent wiping and scrubbing action of said products ofcombustion against said surface, and applying suction for withdrawingthe products of combustion tangentially of said cylinder in a regionextending lengthwise of said cylinder and adjacent said surface.

6. The method of heating a hollow cylinder at rates not limited by thepresence of an insulating layer of air between the curved inner surfaceand products of combustion within said cylinder, which comprisesdirecting burning streams of pre-r'nixed fuel and air at a substantialangle to said curved inner surface along a path which is angularlydisplaced from a radius of said cylinder for development of substantialforward velocity of all of said burning fuel and air and in a zoneextending lengthwise of the cylinder and in close proximity to saidcurved internal surface, constraining the flow path of the burningstreams of pre-mixed fuel and air along said curved inner surface of thecylinder to develop centrifugal forces urging said combustion gasesoutwardly against said curved internal surface, the expansion of thegases incident to the combustion thereof maintaining a high velocity ofsaid gases throughout a large circumferential area of the cylinder,rotating said cylinder to move said curved inner surface in counterflowto said products of combustion to cause the adjacent surface layer ofsaid products of combustion to be in turbulent flow, and applyingsuction for withdrawing the products of combustion tangentially of saidcylinder in a region extending lengthwise of said cylinder and adjacentsaid surface.

7. The method of heating a hollow cylinder at rates not limited by thepresence of an insulating layer of air between the curved inner surfaceand products of combustion within said cylinder, which comprisesdirecting burning streams of pre-mixed fuel and air at a substantialangle to said curved inner surface and in a zone extending lengthwise ofthe cylinder and in close proximity to said curved internal surface,constraining the flow path of the burning streams of pro-mixed fuel andair along said curved inner surface of the cylinder to developcentrifugal forces urging said combustion gases outwardly against saidcurved internal surface, the expansion of the gases incident to thecombustion thereof maintaining a high velocity of said gases throughouta large circumferential area of the cylinder, rotating said cylinder tomove said curved inner surface in counterflow to said products ofcombustion to cause the adjacent surface layer of said products ofcombustion to be in turbulent flow, applying suction for withdrawing theproducts of combustion tangentially of said cylinder in a regionextending lengthwise of said cylinder and adjacent said surface, andregulating the angular spacing between the points of initiation of saidburning streams and said region of withdrawal in accordance with changein flow of said fuel and air.

8. The method of heating a hollow cylinder at rates not limited by thepresence of,an insulating layer of air between the curved inner surfaceand products of combustion within said cylinder, which comprisesdirecting burning streams of pre-mixed fuel and air at a substantialangle to said curved inner surface along a path which is angularlydisplaced from a radial line of said member for development ofsubstantial forward velocity of all of said burning fuel and air and ina zone extending lengthwise of the cylinder and in close proximity tosaid curved internal surface, constraining the flow path of the burningstreams of pre-mixed fuel and air along said curved inner said gasesthroughout a large circumferential area of the cylinder, rotating saidcylinder to move said curved inner surface in counterflow to all of saidproducts of combustion to cause the adjacent surface layer of saidproducts of combustion to be in turbulent fiow, applying suction forwithdrawing the products of combustion tangentially of said cylinder inaregion extending lengthwise of said cylinder and adjacent said surface,and varying the suction pressure at the region of withdrawal inaccordance with change in flow of said fuel and air.

, 9,. Themethod of transferring heat to a load by way of the wall of ahollow cylinder at rates notlimited by the presence of an insulatinglayer of air between the curved inner surface and products of combustionwithin said cylinder, which comprises directing burning streams ofpre-mixed fuel and air at a substantial angle to said curved innersurface along a path which is angularly displaced from a radial line ofsaid member for development of substantial forward velocity of all ofsaid burning ,fuel and air; and in a one extending lengthwise of thecylinder and in close proxiinity to said curved internal surface,constraining the flow path of the burning streams of pre-mixed fuel andair along said curved inner surface .of the, cylinder to developcentrifugal forces urging said combustion gases, outwardly against saidcurved internal surface, the expansion of the gases incident tothecombustion thereof maintaining a high velocity .of said gases throughouta large circumferential area ofthe cylinder,

rotating said cylinder to move said curved inner surface ,in counterflowto said products of combustion tocause the adjacent surface layerof saidproducts of combustion to be in turbulent flow, applying suction forwithdrawing 1 the products ofcombustion tangentially of said cylinder-in a region extending lengthwise of said cylinder and adjacent saidsurface, and concurrently regulating the angularspacing between thepoints of initiation of said burning strem and said region of withdrawaland the suction pressure at the region of withdrawal in accordance withchangein heat load on said cylinder. {10. A heating system comprising ahollow cylinder,

in, fuel burner having a plurality of fuel-'directingjets ,disposedadjacent the concave internal surface of the cylinder and inclined at anangle with respect thereto for imparting to jets of burning pre-mixedfuel and air a large tangential velocity in the region in whichtheburning ,pre-mixed fuel ,and air impinges upon said surface, an exhaustmanifoldwith inlet means distributed along and adjacent said surface,said inlet means dis- 'posed generally tangentially of said cylinder andfacing toward said jets for flow tangentially therein of the prodnets ofcombustion moving along said concave surface,

end;closure members for said cylinder each including a headvhaving acircular array of openings spaced in- I and having, aplurality ofair-impeller elements extending outwardly from said plate for producinga flow of air between the impeller plates and in heat exchange with saidplate and said head,said heat flin'gers terminating in spaced relationwith said journals for producing a flow of air alongv said journals andinto and along the space between saidheat flingers.

11. A heating system comprising a hollow cylinder, a fuel burner havinga plurality of fuel-directing jets disposed adjacent the concaveinternal surface of the cylinder and inclined at an angle with respectthereto for imparting 'tojets of burning premixed fuel and air a largetange'ntial velocity in the region in which the burning pr s-mixed fueland air impinges upon said surface, an exhaust manifold with inlet meansdistributed along and adjacent said, surface, said inlet means disposedgenerally tangentially of said cylinder and facing toward said jets 'forflow tangentially therein of the products of combustion moving alongsaid concave surface, rotary support-iii'gmeans for rotation of saidcylinder about its longitudinal axis, means for rotating said cylinder,a supplypipe for said fuel burner'displaced from said longitudinal axisand extending through said rotary supporting means, said supply pipewithin said cylinder having an offset, a T-fitting connected to saidoffset portion of said supply pipe and located coaxially of saidcylinder, said exit passage being coaxial with said cylinder andincluding a pipe having structureadjacent one end thereof formingwithstructure carried by said T-fitting a bearing, and means for bodilyrotating with respect to each other said fuelburner and said exhaustmanifold.

12. A system "of heating a hollow cylinder for transfer of heat throughthe wall thereof to a heat load, which comprises a fuel burner, meansfor supplying said fuel .ducing flow of said'products of combustion atsubstantial velocity in intimate heat exchange with said internalsurface, means for rotating said cylinder in a direction counter to theflow of said products of combustion for inducing a multiplicity of eddycurrents and swirls within the region adjacent said internal surface toincrease the ,rate ofheat transfer thereto, said angular disposition ofsaid fuel jets and saidcurved inner suiface giving rise tocentrifugal'force's, applying to said swirls and eddy currents forceswhich tend to maintain them in intimate contact with said inner surface,an exhaust manifold with inlet means distributed lengthwise of saidcylinder and adjacent said internal surface of said cylinder, said inletmeans disposed generally tangentially of said cylinder and facing towardsaid jets for flow of said products of combustion into said manifoldadjacent said surface, means for applying suction to said manifold forforced flow of combustion products therein and for development of forcestending to maintain the flow of said combustion gases along said innersurface, and means respo'nsive to the heat load for adjusting saidangular separation in accordance with change in said heat load.

13.,A system of heating a hollow cylinder for transfer of heat throughthe wall thereof to a heat load, which comprises a fuel burner, meansfor supplying said fuel burner with 'pre-mixedfuel and combustion air,said burner having a plurality of fuel-directing jets disposedlengthwise of the cylinder and adjacent the internal surrection counterto the flow of said products of combustio 'for inducing a multiplicityof eddy currents and swirls cylinder and facing toward said jets forflow of said products of combustion into said manifold adjacent saidsurface, means for applying suction to said manifold for forced flow ofcombustion products therein and for development of forces tending tomaintain the flow of said combustion gases along said inner surface,means for relatively adjusting the angular separation between said fuelburner and said exhaust manifold, and means responsive to the heat loadfor adjusting said angular separation in accordance with change in saidheat load and for concurrently adjusting the suction applied to saidmanifold for developing maximum heat transfer for a given rate of fuelsupply to said burner.

14. A system of heating a hollow cylinder for transfer of heat throughthe wall thereof to a heat load, which comprises a fuel burner, meansfor supplying said fuel burner with pre-mixed fuel and combustion air,said burner having a plurality of fuel-directing jets disposedlengthwise of the cylinder and adjacent the internal surface thereof andinclined at an angle for producing along said internal surface flow ofburning fuel and hot products of combustion, the combustion of saidpre-mixed fuel producing flow of said products of combustion atsubstantial velocity in intimate heat exchange with said internalsurface, means for rotating said cylinder ina direction counter to theflow of said products of combustion for inducing a multiplicity of eddycurrents and swirls within the region adjacent said internal surface toincrease 'the rate of heat transfer thereto, said angular disposition ofsaid fuel jets and said curved inner surface giving rise to centrifugalforces applying to said swirls and eddy cur- ,rents forces which tend tomaintain them in intimate contact with said inner surface, an exhaustmanifold with inlet means distributed lengthwise of said cylinder andadjacent said internal surface of said cylinder, said inlet meansdisposed generally tangentially of said cylinder and facing toward saidjetsfor flow of said products of combustion into said manifold adjacentsaid surface, means for applying suction to said manifold for forcedflow of 1 vcombustion products therein. and for development of forcestending to maintain the flow of said combustion y gases along said innersurface, means for relatively adjusting the angular separation betweensaid fuel burner and said exhaust manifold, and means for adjusting thearea'of the internal surface in contact with said hot products ofcombustion in accordance with the magnitude of 7 the flow of fuel tosaid burner and for increasing said area with increase in said magnitudeand for decreasing said-area with decrease of said magnitude.

15. A system of heating a hollow cylinder for transfer of heat throughthe wall thereof to a heat load, which comprises a fuel burner, meansfor supplying said fuel burner with pre-mixed fuel and combustion air,said burner having a plurality of fuel-directing jets disposed length-.wise of the cylinder and adjacent the internal surface thereof andinclined at an angle for producing along said velocity in intimate heatexchange with said internal surface, means for rotating said cylinder ina direction counter to the flow of said products of combustion forinducing a multiplicity of eddy currents and swirls within the regionadjacent said internal surface to increase the rate of heat transferthereto, said angular disposition of said fuel jets and said curvedinner surface giving rise to centrifugal forces applying to said swirlsand eddy currents forces which tend to maintain them in intimate contactwith said inner surface, an exhaust manifold with inlet meansdistributed lengthwise of said cylinder and adjacent said internalsurface of said cylinder, said inlet means disposed generallytangentially of said cylinder and facing toward said jets for flow ofsaid products of combustion into said manifold adjacent said surface,means for applying suction to said manifold for forced flow ofcombustion products therein and for development of forces tending tomaintain the flow of said combustion gases along said inner surface,control means responsive toa temperature at a selected location on saidcylinder for controlling said fuel supply means to increase the rate offuel supply with decrease of temperature and for decreasing said rate offuel supply with increase in said temperature, and control meansresponsive to said change in said rate of said fuel supply forconcurrently varying the area of said internal surface over which saidhot products of combustion flow in heat transfer therewith to increasesaid area with increase in said rate of fuel supply and to decrease saidarea with decrease in said rate of fuel supply.

16. Heat-transfer means comprising a hollow cylinder, means for heatingat least a portion of the internal surface of said hollow cylinder atrates not limited by the presence of an insulating layer of air betweenthe internal curved surface of said cylinder and products of combustionwithin said cylinder comprising a fuel burner for directing burning highvelocity streams of pro-mixed fuel and air at a substantial angle to theinternal curved surface of said cylinder along a path which is angularlydisplaced from a radius of said cylinder for development of' substantialforward velocity of all of said burning fuel and air and in a zoneextending lengthwise of the cylinder and in close proximity to its saidcurved internal surface, said cylinder constraining the flow path oftheburning streams of pre-mixed fuel and air along said curved innersurface whereby the initial velocity of said pre-mixed fuel and air andthe expansion of the gases incident to the combustion thereof maintainsthe high initial velocity throughout a large circumferential area of thecylinder, means including a suction head extending across the armatepath traversed by the products of combustion for applying suction forwithdrawal of the products of combustion tangentially of said cylinderin a region extending lengthwise of said cylinder and adjacent saidsurface, and means responsive to a change in a variable affecting saidrate of transfer of heat to said cylinder, said means including pivotalmounting structure, for relatively angularly-changing the separationdistance between said fuel tel burner and said suction head to regulatethe site of the area over which there is a high rate of transfer of heatto said cylinder..

References Cited in the file of patent UNITED STATES PATENTS 1,240,468Martin Sept. 18, 1917 1,704,875' Vaughn Mar. 12, 1929 1,768,777 Moller'July l, 1930 1,945,273 Hetzer Jan. 30, 1934 2,521,371 Hornbostel Sept.5,1950 2,764,232 Johns Sept. 25, 1956

